John in Mortal Danger = John in Love
Let’s think about this colorful triangle of lavender, green, and yellow/sodium.
The first image is from The Empty Hearse. Sherlock’s just dropped his chips to the floor and is dashing out 221B with Mary just behind. This is right before he steals the motorcycle. The second image is from The Sign of Three. It’s John and Mary waltzing (poorly) after the photographer’s arrest and before Sherlock’s pregnancy deduction and vow to clan Watson.
The color schemes are identical and they link the scenes emotionally and semantically. If the Newlyweds waltzing put you on edge it’s not just because they don’t really know what they’re doing on the dance floor. It likely has to do with the fact that when you last saw those tints in S3, John was in mortal danger.
His heart was to be burned right out of him.
It makes sense. Sherlock claws his way back to life because John is in danger. But riddle me this: what danger is John actually in? I’m not convinced we’ve seen this danger yet. Magnussen put him in a bonfire, but he admits that he didn’t intend to actually kill him in there. If Mary and Sherlock hadn’t worked it out, Magnussen would have had his people save John. Mary seems pretty intent on keeping John out of her nonsense. There’s all these clues and threats about John being in danger, but no actual danger has presented itself to date. At the moment, John looks like the safest, most well-insulated man in Europe. He has Sherlock looking out for him, his own private assassin, and he’s pretty handy with a tire lever to boot.
Are they working up to some unthinkable incident where the danger John is in becomes terrifyingly apparent? Will it be something that Sherlock tries desperately to stop and fails, causing John some real bloodshed and leaving Sherlock momentarily and erroneously convinced that John is dead? Will this then quite naturally lead to some intense show of emotion and affection from Sherlock that John comes to consider, shall we say, worth a wound?